Environmental impacts of abandoned dredged soils and sediments

Abstract

In the process of creating safe navigable waterways for oil exploitation, the companies operating in the Niger Delta generate tons of sulfidic spoils. These are often deposited over bank, mostly upon fringing mangroves, and abandoned. This leads to a myriad of environmental problems. The extent of these impacts is not exactly known, but was inferred from the activities of oil companies operating in the area. This paper describes the impacts following the disturbance of sulfidic sediment through dredging and by subsequent poor spoil management practices. Environmental impacts of exposed and abandoned sulfidic sediments. The practice of dumping and abandoning sulfidic dredged spoils along canal banks triggers a series of environmental problems leading to extreme acidification, heavy metal pollution, and general habitat degradation which prevent the re-colonization of the sites by native species. The resultant spoil dumps remain bare for several years and they become colonized by invasive species later. Later still they may become attractive to the local population as sites for houses, fishing camps and home gardens, which is nevertheless regarded as a positive impact. Management of abandoned sulfidic spoil dumps. As a panacea to environmental problems caused by the sulfidic spoils, they need to be properly handled to prevent their acidification. This should be followed by mangrove restoration to pristine conditions or rehabilitation to other beneficial uses. Conclusion and Recommendation. The abandoned sulfidic spoils in the Niger Delta have resulted in the death of several thousands of hectares of mangrove habitat and their associated biota. Despite the increasing scale of dredging and spoil abandonment, the accompanying problems have been recognized by neither the oil companies nor by national government. This paper attempts to highlight these problems and concludes by recommending sound spoil management strategies involving the handling, restoration and rehabilitation of impacted areas. Furthermore, possible beneficial use of dredged spoils for civil construction, beach nourishment / shoreline protection is identified. The Nigerian Government needs to promulgate and enforce laws that will permit the sustainable use of mangrove resources.